At least four explosions were heard Monday night around outdoor bars in the Sabon Gari area of Kano, causing panic and sending clouds of smoke and dust into the air, residents said. One resident said a small church may have also been among the targets.
The military blamed the attack on suspected members of Islamist extremist group Boko Haram and said packages that caused the explosions were left in the area.
Nigeria's military has been waging a sweeping offensive in the country's northeast in a bid to end Boko Haram's four-year insurgency.
Kano, a major commercial centre in Nigeria's predominantly Muslim north, is not in the area targeted by the offensive. It has recently seen a lull in attacks, though it has previously been hit by heavy violence blamed on Boko Haram. "We have at the moment 24 dead bodies in our morgue and three patients in our emergency ward from the explosions in Sabon Gari last night," said Aminu Inuwa, spokesman for the Aminu Kano Teaching Hospital in Kano.
"The dead had shrapnel wounds on them."
Residents described the area as being littered with the personal belonging of those who ran in fear once the explosions began. "There is confusion all over the place," Chinyere Madu, a fruit vendor, said on Monday night. "There were four huge explosions, so huge that they shook the whole area."
She said she saw "one person carrying someone on his shoulders with bleeding legs." "My house is not far from there," resident Kola Oyebanji told AFP. "All my windows are shattered."
Another resident Idika Tobias told AFP he had visited the blast site and stood amid a litter of personal effects left behind by people fleeing. "Shoes, bags, cellphones" and other items were scattered around, he said.
A small church sandwiched between two bars appeared to be among the targets, Tobias added.
Boko Haram, which has carried out waves of bombings across northern Nigeria, was blamed for coordinated suicide blasts at a bus park in Sabon Gari in March that killed at least 41 people. Kano has been among the cities hardest hit during Boko Haram's insurgency, despite the recent lull.
Following a massive coordinated gun and bomb assault in January 2012 that killed at least 185 people, security forces blanketed the city, setting up checkpoints at many roundabouts and intersections.
Nigeria launched an offensive against Boko Haram in May, specifically targeting three states to the east of Kano. Since then, the security forces have claimed huge gains against the insurgents, insisting that they have put them on the defensive. Attacks eased after the offensive began but the bloodshed has persisted in some areas.
At least three schools have been attacked in northeastern Nigeria by suspected Boko Haram members in recent weeks.
Over the weekend, clashes between a vigilante group and Boko Haram members left at least 20 people dead in the village of Dawashe in Borno state.
The insurgency is estimated to have claimed more than 3,600 lives since 2009, including killings by the security forces.
Nigeria, Africa's most populous nation and largest oil producer, is roughly divided between a mainly Christian south and mostly Muslim north.